/*
 * Copyright (c) 2011-2025, The DART development contributors
 * All rights reserved.
 *
 * The list of contributors can be found at:
 *   https://github.com/dartsim/dart/blob/main/LICENSE
 *
 * This file is provided under the following "BSD-style" License:
 *   Redistribution and use in source and binary forms, with or
 *   without modification, are permitted provided that the following
 *   conditions are met:
 *   * Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *   * Redistributions in binary form must reproduce the above
 *     copyright notice, this list of conditions and the following
 *     disclaimer in the documentation and/or other materials provided
 *     with the distribution.
 *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
 *   CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
 *   INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 *   MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *   DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
 *   CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 *   SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 *   LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 *   USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 *   AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 *   LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 *   ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 *   POSSIBILITY OF SUCH DAMAGE.
 */

#include "dart/gui/RealTimeWorldNode.hpp"

#include "dart/common/Logging.hpp"
#include "dart/simulation/World.hpp"

#include <algorithm>

namespace dart {
namespace gui {

//==============================================================================
RealTimeWorldNode::RealTimeWorldNode(
    const std::shared_ptr<dart::simulation::World>& world,
    const ::osg::ref_ptr<osgShadow::ShadowTechnique>& shadower,
    const double targetFrequency,
    const double targetRealTimeFactor)
  : WorldNode(world, shadower),
    mFirstRefresh(true),
    mTargetRealTimeLapse(1.0 / targetFrequency),
    mTargetSimTimeLapse(targetRealTimeFactor * mTargetRealTimeLapse),
    mLastRealTimeFactor(0.0),
    mSimTimeBudget(0.0),
    mLowestRealTimeFactor(std::numeric_limits<double>::infinity()),
    mHighestRealTimeFactor(0.0)
{
  // Do nothing
}

//==============================================================================
void RealTimeWorldNode::setTargetFrequency(double targetFrequency)
{
  const double targetRTF = mTargetSimTimeLapse / mTargetRealTimeLapse;
  mTargetRealTimeLapse = 1.0 / targetFrequency;
  mTargetSimTimeLapse = targetRTF * mTargetRealTimeLapse;
}

//==============================================================================
double RealTimeWorldNode::getTargetFrequency() const
{
  return 1.0 / mTargetRealTimeLapse;
}

//==============================================================================
void RealTimeWorldNode::setTargetRealTimeFactor(double targetRTF)
{
  mTargetSimTimeLapse = targetRTF * mTargetRealTimeLapse;
}

//==============================================================================
double RealTimeWorldNode::getTargetRealTimeFactor() const
{
  return mTargetSimTimeLapse / mTargetRealTimeLapse;
}

//==============================================================================
double RealTimeWorldNode::getLastRealTimeFactor() const
{
  return mLastRealTimeFactor;
}

//==============================================================================
double RealTimeWorldNode::getLowestRealTimeFactor() const
{
  return mLowestRealTimeFactor;
}

//==============================================================================
double RealTimeWorldNode::getHighestRealTimeFactor() const
{
  return mHighestRealTimeFactor;
}

//==============================================================================
void RealTimeWorldNode::refresh()
{
  customPreRefresh();
  clearChildUtilizationFlags();

  if (mNumStepsPerCycle != 1) {
    DART_WARN(
        "[RealTimeWorldNode] The number of steps per cycle has been set to "
        "[{}], but this value is ignored by the RealTimeWorldNode::refresh() "
        "function. Use the function "
        "RealTimeWorldNode::setTargetRealTimeFactor(double) to change the "
        "simulation speed.",
        mNumStepsPerCycle);
    mNumStepsPerCycle = 1;
  }

  if (mWorld && mSimulating) {
    if (mFirstRefresh) {
      mRefreshTimer.setStartTick();
      mSimTimeBudget = 0.0;
      mFirstRefresh = false;
    }

    const double startSimTime = mWorld->getTime();
    const double simTimeStep = mWorld->getTimeStep();
    const double elapsedRealTime = mRefreshTimer.time_s();
    const double targetRTF = getTargetRealTimeFactor();

    if (targetRTF > 0.0 && elapsedRealTime > 0.0)
      mSimTimeBudget += elapsedRealTime * targetRTF;
    else if (elapsedRealTime <= 0.0)
      mSimTimeBudget += mTargetSimTimeLapse;

    std::size_t numSteps = 0;
    const std::size_t maxStepsPerRefresh = 2048;
    while (simTimeStep > 0.0 && mSimTimeBudget + 1e-12 >= simTimeStep
           && numSteps < maxStepsPerRefresh) {
      customPreStep();
      mWorld->step();
      customPostStep();
      mSimTimeBudget -= simTimeStep;
      ++numSteps;
    }

    if (numSteps == maxStepsPerRefresh) {
      DART_WARN(
          "[RealTimeWorldNode] Reached step limit during refresh; simulation "
          "may be lagging behind real time.");
      mSimTimeBudget = 0.0;
    } else if (mSimTimeBudget < 0.0) {
      mSimTimeBudget = 0.0;
    }

    const double simAdvanced = mWorld->getTime() - startSimTime;
    const double denominator
        = (elapsedRealTime > 0.0) ? elapsedRealTime : mTargetRealTimeLapse;

    if (denominator > 0.0)
      mLastRealTimeFactor = simAdvanced / denominator;
    else
      mLastRealTimeFactor = 0.0;

    mLowestRealTimeFactor
        = std::min(mLastRealTimeFactor, mLowestRealTimeFactor);
    mHighestRealTimeFactor
        = std::max(mLastRealTimeFactor, mHighestRealTimeFactor);

    mRefreshTimer.setStartTick();
  } else {
    mFirstRefresh = true;
    mSimTimeBudget = 0.0;
  }

  refreshSkeletons();
  refreshSimpleFrames();

  clearUnusedNodes();

  customPostRefresh();
}

} // namespace gui
} // namespace dart
